Trayvon Martin case: Martin was the aggressor, police sources say

As Florida braced itself for what could be the biggest day of protest yet in the Trayvon Martin case, police revealed new details that depict the slain 17-year-old as the aggressor and appear to support George Zimmerman's claim that he was acting in self-defense when he shot the teenager.

Martin was killed one month ago today. That's one month of justice denied, according to protesters who are expected to amass throughout the day to continue their demand for Zimmerman's arrest in the Sanford, Fla. case.

A forum hosted by CNN commentator Roland Martin is being held at noon today in that city, followed by a 4 p.m. rally that is expected to draw thousands. Civil rights activist Jesse Jackson plans to lead protesters to the Sanford City Commission meeting being held this evening, and attended by the slain teen's parents. And students at Florida State University, the University of Florida and Florida A&M University will hold rallies on their campuses.

Meanwhile, police have revealed new details surrounding the case that has captured national attention, reigniting the race debate in America.

The Orlando Sentinel is reporting that police sources say Martin was the aggressor on Feb. 26, knocking Zimmerman to the ground with a single punch and then climbing on top of the 28-year-old neighborhood watch captain and slamming the back of his head into the ground. Police say this account, given by Zimmerman, is supported by eyewitnesses, according to the Sentinel's report.

One such witness reportedly told police that he saw Martin on top of Zimmerman, striking the man, while Zimmerman cried out for help. The attack left Zimmerman bloodied, police sources told the Sentinel, and led him to fire at Martin in self-defense.

Police say Zimmerman was bleeding from the nose, had a fat lip and confirm that the back of his head was cut. He received first aid at the scene but refused to go to the hospital and received medical treatment the following day, according to the Sentinel's sources.

The Sentinel's story also makes public new details about the circumstances leading up to the deadly confrontation between Zimmerman and Martin.

At the time, Martin was suspended from high school after he was found to be in possession of an empty marijuana baggie, according to the Sentinel. Martin's school has a "zero-tolerance" drug policy, the newspaper added.

Zimmerman was heading to the grocery store when he spotted Martin and called police to report a black youth acting suspiciously, possibly on drugs.

Zimmerman stepped out of his SUV to follow Martin, even though a police dispatcher told him he didn't need to do so.

Zimmerman told police he he'd lost sight of Martin and was heading back to his car when the youth suddenly stepped into his path. According to the Sentinel, Martin asked Zimmerman if he had a problem. Zimmerman said no and reached for his cellphone. Martin then said something like, "Well, you do now" and punched him, according to the Sentinel's sources.